add update_master_signatures

src/syntax.ml

@@ -4,6 +4,9 @@ let ( let+ ) o f = match o with Ok v -> Ok (f v) | Error _ as e -> e
 (* TODO use polymorphic variant for errors *)
 let unwrap_err_msg o = match o with Error (`Msg e) -> Error e | Ok v -> Ok v
 
+let unwrap_err_caqti o =
+  match o with Error err -> Fmt.error "%a" Caqti_error.pp err | Ok v -> Ok v
+
 let list_iter f l =
   let err = ref None in
   try